Many airbag restraint systems have a panel containing an integral deployment door which covers; and conceals an airbag assembly in an internal portion of a vehicle, e.g., a vehicle instrument panel, door panel, or side panel. The integral deployment door is caused to open during the inflation of the airbag to provide a doorway outlet through the panel by which the inflating airbag deploys into the vehicle passenger compartment. The panel includes a tear seam or region serving as a boundary or edge of the deployment door and which integrally joins the deployment door with the remaining areas of the panel. During airbag deployment, the deployment door is detached or separated from the remaining panel along the tear region for opening the door outlet and thus permitting the inflating airbag to enter the passenger compartment of the vehicle to protect its occupants.
In order to cause the deployment door to open, a tear means, such as a cutter and/or ripper, is generally aligned with the tear region. The inflating force of a deploying airbag drives the tear means through the tear region to separate the deployment door from the rest of the panel. The deployment door is generally hinged along an edge thereof or tethered to an interior substrate of the vehicle, such as the instrument panel, to prevent the total release of the door into the passenger compartment since flying objects and debris in the passenger compartment must be avoided for the passenger's safety.
The panel in which the deployment door is contained normally comprises a vinyl outer layer separated by foam core from a metal or thermoplastic substrate. Accordingly, the tear means must tear through the foam core and vinyl covered surface of the panel in order to open the deployment door. Such action will generally cause fragmentation of the foam which fragments can be expelled into the passenger compartment. The thicker the region between the tear means and the tear seam, the greater the force which will be required to open the deployment door and the greater the amount of debris that can be created in the deployment process.